Size-tunable Pt nanoparticles assembled on functionalized ordered mesoporous carbon for the simultaneous and on-line detection of glucose and L-lactate in brain microdialysate

This study presents a facile electrochemical method for simultaneous and selective on-line detection of glucose and L-lactate in the striatum of anesthetic rats through the integration of selective electrochemical detection with in vivo microdialysis system. A positively-charged polyelectrolyte, (diallyldimethylammonium chloride) (PDDA), was attached onto carbon mesoporous material (CMM) through non-covalent interaction, which provided an ideal environment for the assembling and dispersion of nanoparticle electrocatalysts. Platinum nanoparticles with wide loadings from 5 to 50 wt% were successfully self-assembled on PDDA-functionalized CMM via electrostatic interaction. TEM results showed that with the increase in the Pt loadings, both the size and interconnectivity between particles increased, with particle sizes ranging from 3.2 +/- 0.4 to 6.8 +/- 1.4 nm. Moreover, the electrocatalytic activities of the as-prepared six Pt/PDDA-CMM hybrid nanocomposites were also observed to show an inverted-V-shaped profile as a function of loading amount of Pt NPs. Integrated with glucose oxidase (GOx), L-lactate oxidase (LCD) and the in vivo microdialysis system, the constructed dual oxidase/Pt/PDDA-CMM/Nafion biosensors were successfully applied for the simultaneous and on-line detection of glucose and L-lactate. After post-calibration, the basal level of glucose and L-lactate in the striatum of anesthetic rats was calculated to be 0.27 +/- 0.03 and 0.71 +/- 0.05 mM (mean +/- s.d., n=3), respectively. What is more important, the dual oxidase biosensors almost suffered from little cross-talk, which is characteristic of an excellent sensor with high performance. This property, along with the good linearity and a high stability substantially enables this method promising application in physiology and pathology. (C) 2012 Published by Elsevier B.V.